Conference decwet::windows-nt

5911.0. "Virtual Memory Problem in WNT4.0" by QCAV01::CHENTHIL () Tue Apr 15 1997 06:25

Our application basically converts CAD data which are spread across
multiple files and formats to ONE single file in a custom format.
Also, the application allows the user to view CAD data graphically and
permits the user to edit them. Initially the software was developed for
Windows NT 3.51. While we were able to run the same binary of the application
successfully in Windows NT 4.0 for some CAD data files, we had virtual
memory problem for others.

On examination,

We have observed that the Win32 call CreateCompatibleBitmap fails on
Windows NT 4.0 when the nWidth and nHeight parameters are large. 
On Windows NT 3.51 this call creates bitmaps as large as the available
page file. But on Windows NT 4.0, the largest bitmap we can create
is about 40MB. We have 250MB page file for both 3.51 and 4.0.

Please let us know whether there are any limitations in 4.0.

Run time environment
--------------------

        System                          : Pentium PC - 100MHz
        Operating system                : Windows NT 4.0
        Main memory                     : 16MB/32MB
        Free Hard disk space            : > 400 MB (Capacity : 1 GB)
        Configured Virtual Memory space : Min 250 MB, Max 250 MB
        Active applications             : None other than our application
        Display adapter                 : Diamond Shealth 64 DRAM
                                          with colors set to 64K colors
                                          and resolution of 800x600


Development tools used  :  Borland C++, zAPP libraries


    
    Any ideas about this problem? Is this a known issue? Then how do I
    resolve it?
    
    Regards,
    CHENTHIL
    

I am experiencing the same behaviour.

In order to appply patches to BC++ 5.0 I use the supplied PATCH.EXE which I
run 
from a DOS window under WNT 4.0 with SP2.

I observe the following when I run the program with only the Task Manager
active:
  * in the Performance window of the Task Manager the virtual memory index
grows 
    with linear fashion
  * the average execution time for each file patched is *normal* when the
virtual
    memory is about less than twice the physical memory (in my case I have
32MB
    of RAM) but it goes to *4Hours!!* when the used virtual memory is greater
    then 64MB

When the PATCH.EXE program terminates (until now because I kill it with ^C)
the
used virtual memory returns to the level it was before I ran the program.

I have installed the HOTFIXes post SP2 but that did not fix the problem.

From a colleague I have heard that there should be an hotfix for this, but a 
research on the microsoft site did not show any indication of its existence.

    Costantino Balletta
[Posted by WWW Notes gateway]

In Microsoft TechNet document PSS ID Number Q158142 it states that the 
WM_DDE_EXECUTE API causes a memory leak in the WOW subsystem and that the 
fix is in the latest SP.

Indeed I applied a preliminary version of SP3 which alleviate the pain 
(i.e. the memory leak seems to be lesser) but it is not a 100% solution 
in my case.
[Posted by WWW Notes gateway]